@Eric Tucker - In addition to salesmen giving clocks to power stations, there was a more formal version: the Warren Telechron Master Clock: A very accurate clock movement driving one hand on a clock dial, while a synchronous motor drove an additional hand, so they just had to adjust the generator frequency to keep the one hand on top of the other.

Hi Rob. Actually the "machine" is a telephone. The Naval Observatory (USNO) in Washington at the time had 27 atomic clocks of various types that were located around in closets, rooms, etc (to account for room temp variations). The time from each clock was averaged and fed to a rack mounted thing called a Nano Clock (I forget who made those) the output of the Nano Clock went to an announcing machine (of which I designed part of) that stored phrases like the words "one", "two", "u. s. naval observatory time is", etc. When you call the USNO telephone number a Weatherchron announcer seizes the line and on the next cycle that starts every five seconds (I think) assembles the words into a complete phrase that sounds resonably natural.

The "voice announcer" number is on the USNO website and anyone can call it (including jewelers). The machine has been in service for several decades pretty much non-stop.

The machine was designed way back when UV erasable EPROMs were common and the voice was stored in a bank of Eproms in 8 bit telephone CODEC format.

The man who owned the company died a couple of years ago and was one of the smartest people I've ever known, and one of the best friends I ever had. He knew (as far as I could tell) just about everything about everything. The DAY AFTER the space shuttle disaster, he told me that the problem was the O-ring seals on the engine. He studied and read just about everything technical he could get his hands.

He would some times look at something I had designed and ask "If this was an airplane would you fly on it?" at which point I would usually make some changes.

The station I worked for had Western Union clocks in the studios. They reset to the correct time once an hour and you could see the second hand either speeding up or holding at the same spot for 2-3 seconds each hour, around 10 minutes before the hour. The sync signal was sent via a dedicated phone line if I understand correctly. We joined the ABC Entertainment Network on the half hour and the clock was always within 1/2 second. (BTW, it was WCWA-AM/FM when I started after high school, the call on FM changed to WIOT and format went to progressive rock from elevator music before I graduated)

Since the network sent a tone 10 seconds prior to the start and went silent for the time before the news started, you could simply open the switch to the mixer board once the tone stopped and the news started (whether you were ready or not). We did also need an ID in that time period as well. I hit the net fairly well while I worked the board but sometimes... the post brings back memories.

A friend of mine got a Rolex for his birthday from his wife one year. After wearing itfor a few days he noticed it was running a few second slow. He returned it to the store to complain and the gentleman explained that he must have been mistaken and that every Rolex they sold was checked against the time standards at the U.S. Naval Observatory in Washington. My friend then explained to the man behind the counter that he BUILT the machine that the store was using to test the watches.

The areas of Japan generally southwest of Kyoto are 60Hz, while the rest of the country is 50Hz. http://en.wikipedia.org/wiki/File:Power_Grid_of_Japan.svg It was the result of the US and England helping rebuild the power grid after WW2. Pretty incredible for a modern industrial nation to have 2 line frequencies! Back-to-back AC/DC/AC converters create the intertie between the two (dotted lines on the map in the link).

The US has 3 major, separate grids with a DC intertie in West Texas between them. But the isolation is not due to frequency differences. I believe the grids are kept in pretty close phase sychronization.

Since AC clocks in Japan had to have motors and gearing compatible with the line frequency, they perfected the ubiqitous AA battery-powered wall clock movement.

My dad grew up in the LA area, which was 50Hz until the late 1940's. I remember him talking about the power company taking clocks and converting or trading them for 60Hz operation.

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